The present invention relates generally to fluid processing and, more particularly, to process instruments. Specifically, the invention concerns the alignment of wafer-style devices installed in a flow line.
Process instruments are used in a wide range of fluid handling systems. While the present invention will be described in the context of a flow measurement device, it is to be understood that the invention could be applied to other types of wafer-style process instruments. Flow measurement devices are used to monitor and control the flow rate or quantity of process flow within a conduit and come in many varieties, including positive displacement and magnetic flow meters, suited for use in numerous applications. The different types of meters employ technology based on the system in which they are installed. For example, a magnetic flow meter is advantageous when the use of moving parts within a flow line is not ideal or practical. While the present invention will be described in the context of a magnetic flow meter, it is to be understood that the invention could be applied to other types of flow meters.
Standard flow meters are interposed between upstream and downstream pipes, each pipe having an end flange. In order to secure the device between the pipes, traditional flow meters are equipped with a flange on each end, each flange having a circle of bolt holes that aligns with bolt holes on the end flanges of the pipes. While flow meter flanges ensure the flow passage of the meter is centered with respect to the flow passage of the conduit, flanged flow meters are relatively large and expensive. Moreover, there a number of possible bolt hole patterns in existing flanged pipelines, requiring flanged flow meters to have distinct bolt hole circles. One solution to reduce cost and simplify installation is to remove the flanges from the flow meter body. While flangeless, or wafer-style, flow meters save money and time, without bolt hole circles on the flanges, these meters can suffer from misalignment issues giving rise to local turbulence and inaccurate meter readings.
Current methods of resolving flow meter alignment issues include providing camming devices positioned between the pipe flanges and the flow meter body during the installation process. Such devices take advantage of existing hardware used to bridge the gap between the upstream and downstream pipes. By rotating camming devices with respect to the flow meter body, the bolts are forced to their extreme positions within the bolt holes, thus ensuring the flow passage of the meter is centered with respect to the flow line. Examples of existing alignment devices are disclosed in U.S. Pat. No. 4,345,464 and U.S. Pat. No. 5,632,632. While these devices can be used to center wafer-style flow meters installed in flanged pipelines having a variety of bolt hole patterns, the additional hardware is problematic both from a production and installation standpoint. Not only is the added equipment less cost-effective and more time-consuming than it could be, the additional hardware, such as camming sleeves or rings and the gaskets required to seal the flow meter between the pipe ends, can easily be ineffectively installed or inadvertently discarded.